Measure the window portion of your French door and add 2 inches to the width and at least 3 inches to the height. This ensures that the outside mounted shades that you order will be the right size. Outside mount shades, whether they are cellular shades, Roman shades or vertical blinds, give your French doors the correct profile and also a pleasing shape
Hold the outside mount shade over the French door window, centering it so that it falls the way you wish.
Mark the position and height of the outside mount shade using a pencil.
Position the brackets slightly below the top edge of the area where the outside mount shade should be, and secure them to the door above the the windows using screws and an electric drill.
Snap the shades to the brackets. The part of the shades that is held by the brackets is known as the headrail, and it is typically secured to the brackets by pressure, though sometimes there are screws involved.